The Public Switched Telephone Network (PSTN) was originally designed for carrying analog voice communication signals. However, users are increasingly using the PSTN to transmit digital data. A typical PSTN network includes numerous central offices. Communication between the central offices can be accomplished through high speed switched digital links. Local loops couple the central offices to the customer premises. The local loops can be analog networks of twisted pair copper wiring. These analog local loops are often referred to as the Plain Old Telephone System (POTS). A "customer premises network", "premises network", or "premises wiring" typically connects electronic devices within the customer premises to the local loop. For example, a typical premises network can comprise twisted pair wiring coupled to RJ-11 phone jacks.
The central office typically includes, among other elements, a bandpass filter that can limit the bandwidth of the local loop to approximately 3.3 kHz (between 300 Hz and 3.4 kHz). This is done so that numerous voice-grade local loop lines can be digitized and multiplexed together for transmission between central offices over the switched digital links.
Current computing environments necessitate the need for digital transmission of data. Several services such as leased or switched lines enable such data traffic, but can be prohibitively expensive. Similarly, replacing the telephone infrastructure with a medium that is more conducive to digital traffic can also be prohibitively expensive. Therefore, users desire to use POTS lines to transmit digital data.
Conventional modem technology is one such method of transmitting digital data over POTS lines. This technology attempts to transmit high speed data over POTS lines within the limits of the allocated voice bandwidth, or below 3.4 kHz.
Digital Subscriber Line (xDSL) technology, on the other hand, can apportion the transmission of data over POTS lines into a voice channel and a digital channel. The voice channel can include signals below 4 kHz while the digital channel can include signals above 4 kHz. As such, xDSL can provide a method to increase the bandwidth of the existing telephone network infrastructure. Furthermore, xDSL technology can allow conventional electronic devices that use the voice channel, and xDSL devices such as transceivers, to couple to the same POTS network. Furthermore, the conventional devices and the xDSL devices can communicate simultaneously over the same wiring, using the respective channels. To accomplish this task, splitters or filters can be used to separate the two channels. Typically, a splitter or filter is placed both at the central office and the customer premises of an xDSL network.
One conventional filter architecture used at the customer premises end of an xDSL network is a distributed filter. With a distributed filter architecture, a low pass filter is coupled between the premises network and each electronic device that uses signals in the voice channel. For example, each telephone, facsimile machine, and other conventional telephony device would be coupled first to a low pass filter which would then be coupled to the telephone network of the customer premises (e.g., via a standard telephone line). Each low pass filter allows signals in the voice channel to travel to and from the conventional devices, while filtering out traffic and noise that can be caused by devices using the digital channel. In this scheme, devices using the digital channel, such as xDSL transceivers, can connect directly into the premises network.
Conventional distributed filter systems typically couple a box containing a low pass filter between a wall mount outlet and each conventional electronic device. However, such conventional systems can be disadvantageous because they involve an additional piece of electronic equipment. Such equipment can be positioned in the open, and can be interfered with, for example, by passing foot traffic. Such conventional systems can also require additional monitoring to ensure that the low pass filter box does not become uncoupled from the wall mount outlet.